Generation of high energy density by fs-laser-induced confined microexplosion

Abstract

Confined microexplosion produced by a tightly focused fs-laser pulse inside transparent material proved to be an efficient and inexpensive method for achieving high energy density up to several MJ per cm 3 in the laboratory table-top experiments. First studies already confirmed the generation of TPa-range pressure, the formation of novel super-dense material phases and revealed an unexpected phenomenon of spatial separation of ions with different masses in hot non-equilibrium plasma of confined microexplosion. In this paper, we show that the intense focused pulse propagation accompanied by a gradual increase of ionization nonlinearity changes the profile and spectrum of the pulse. We demonstrate that the motion of the ionization front in the direction opposite to the pulse propagation reduces the absorbed energy density. The voids in our experiments with fused silica produced by the microexplosion-generated pressure above Young's modulus indicate, however, that laser fluence up to 50 times above the ionization threshold is effectively absorbed in the bulk of the material. The analysis shows that the ion separation is enhanced in the nonideal plasma of microexplosion. These findings open new avenues for the studies of high-pressure material transformations and warm dense matter conditions by confined microexplosion produced by intense fs-laser.

Femtosecond laser induced phenomena in transparent solid materials: Fundamentals and applications

“…The spatial separation of Al and O ions under conditions of complete confinement is proposed to be responsible for the generation of high pressure bcc Al [444,448,450,451]. The femtosecond laser pulses with intensity above the optical breakdown threshold break bonds of Al 2 O 3 and ionize Al and O atoms into plasma, which exists until the material cools down to a temperature below the thermal ionization threshold.…”

“…The total separation is about 32 nm between the elements, which is sufficient for formation of the Al nanocrystals. Especially, Gamaly et al reveal that with laser fluence up to 50 times higher than the ionization threshold, the energy can be effectively absorbed in the bulk of the material, resulting in an enhanced ion separation in the non-ideal plasma of microexplosion [451]. Furthermore, the separation of the constituents is confirmed by the observation of molecular oxygen [371,382,452].…”

Selective localised modifications of silicon crystal by ultrafast laser induced micro-explosion

“…Silicon crystal was exposed to strong shock wave induced by fs-laser micro-explosion in confined geometry 20 . Figure 1 shows a schematic representation of the process and the realization of array of voids using focusing fs-pulses at the Si/SiO 2 interface.…”

Laser-plasma induced shock waves in micro shock tubes

“…Here, a single pulse or multiple intense laser pulses are usually focused to a small volume onto a solid target, and then a shock wave occurs and propagates into the target. Related experiments are performed to investigate high energy density physics (HEDP) [4] with special attention to the equation of state (EOS) [5], inertial confinement fusion (ICF) [6] and astrophysics [7]. Experiments in HEDP rely on very high concentration of energy in a small volume, which usually leads to high density, temperature and pressure.…”